﻿// Copyright (c) 2012, Alexander Endris
// All rights reserved.
// 
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
// * Redistributions of source code must retain the above copyright
//    notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above copyright
//    notice, this list of conditions and the following disclaimer in the
//    documentation and/or other materials provided with the distribution.
// 
// THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
// IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
// OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
// IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
// NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
// THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

#region Usings

using System.IO;

#endregion

namespace NamelessOne.Imaging.IO
{
  /// <summary>
  ///   A reader that reads single bits in a byte stream (Needed for huffman coding)
  /// </summary>
  internal class BitReader
  {
    #region Public / Constructors

    public BitReader(BinaryReader reader)
    {
      this.reader = reader;
      position = -1;
    }

    #endregion

    #region Public / Methods

    public static bool GetBitValue(long buffer, int bitCount, int position)
    {
      position = bitCount - position - 1;

      return ((buffer >> position) & 0x1) == 1;
    }

    public bool ReadBit()
    {
      if (position == -1)
      {
        if (reader.Peek() != -1)
        {
          buffer = reader.ReadByte();
          while (buffer == 0xFF && reader.Peek() != 0)
          {
            reader.ReadByte();
            buffer = reader.ReadByte();
          }
          if (buffer == 0xFF)
            reader.ReadByte();

          position = 7;
        }
        else
          throw new EndOfStreamException();
      }

      return ((buffer >> position--) & 0x1) == 1;
    }

    public void Reset()
    {
      position = -1;
    }

    #endregion

    #region Private / Attributes

    private byte buffer;
    private int position;
    private BinaryReader reader;

    #endregion
  }
}